Process of recovery of plating metal from scruff



Dec. 10, 1940- w. J. BULLOCK PROCESS OF RECOVERY OF PLATING METAL FROM SCRUFF Filed Jan. 20, 1940 Hea-fing Ana Agha-Hny Tank Burners Remaining Solids Dress Flee/Viewal To Mold;

May/wile 5 ,1

epqra or 35*5002, Ash per 000* Dross & 2

[NVENTOR BY W/LL/HM J. BULLOCK .ggzfi Zm f2 44,021? ATTO NEYS Peyerb.

Furnace Patented Dec. 10, 1940 a UNITED STATES PROCESS or RECOVERY OF mme METAL mom SCRUFF William J. Bullock, Birmingham, Ala... asslgnor to W. J. Bullock, Inc., a corporation of Delaware Application January 20, 1940, Serial no. 314,886 2 Claims. (Cl. 75-64) My invention relates to the recovery of plating metal from scruff such as is accumulated in sheet metal plating processes wherein the sheets are dipped into molten plating metal.

It is the principal object of my invention to provide a process for the recovery of terne metal from scruff, which shall be simple and economical and by -means of which the percentage of recovery shall be greatly increased.

A further object of my invention is the provision of a process for therecovery of terne metal from scruff which shall greatly reduce the furnace reduction treatment heretofore practiced in prior art processes and which shall also reduce the volatilization losses of metal.

As is well known, there are considerable losses of metal in plating processes and the metal, in

the form of prills, oxides and chlorides is mixedwith iron scrap, sawdust, sweepings, and oil and grease making up the scruff. The term metal content of the scruff may vary from 20%v to 50%. t

It has heretofore been the practice to burn the combustible matter out of the scrufi in a scruff scruff with a caustic alkali solution, leaving a wet sludge containing the free metal, oxides, and a considerable amount of sawdust and other solid matter which is dried on an open dry plate. I may also employ in the alkali solution from 1% to 2% of a petroleum distillate to aid in dissolving the oils and greases. As the water is driven off on the dry plate, the temperature of the dried mass increases and the combustible matter therein finally ignites, sweating the free metal out of the mass and leaving an ash containing principally the oxides of the metal. This ash, after separation of metallic iron, is then treated in a reverberatory furnace with suflicient carbon, preferably in the form of anthracite, to reduce the oxides to metal. By this process I can control the initial temperatures at which the metal is sweated out of the scruff and thus prevent losses and also reduce materially the amount of ash to be treated in the reverberatory furnace. I have found that the recovery of proved process.

metal is increased approximately 10% by my'lmproved method. i r In the accompanying drawing, the singlefigure is a flow sheet showing the'stepsin'my im- Referring tothe ,drawing,,-I charge a heating and agitating tank 10 equipped with a stirrer II 'with one ton of scrufl consisting principallyof sweepings, greasy, oily sawdust, metal prills,

oxides and chlorides. To this is added sufilcient alkali to saponify the oils and greases,

which amounts ordinarily toaround 30 pounds of caustic soda, 70 gallons, or 560 pounds, of water,

and approximately one gallon of a petroleum distillate to aid in dissolving the oil and grease out of the sawdust and sweepings. V

The heating and agitating tank is provided with suitable heating means, such as the gas burners l2, and the mixture is raised to the boiling temperature of the water while vigorously agitating to bring about the reaction between the caustic soda and the saponifiable oils.

.The soluble oil assists during this time in separating the heavier oils from the sawdust. The reaction should be complete in approximately two hours. The saponifled oils and separated greases rise to the surface of the mixture and are skimmed off from the surface. The remainder of themixture is then drained through the valve I3 into the settling tank II. The operation just described also dissolves out the zincammonium chloride which accompanies the scrufi as an impurity.

The mixture drained into the settling tank [4 consists of the substances carried in solution by the alkaline liquor, the sawdust, oxides, and tree metal content of the scruff. The mixture is allowed to settle for about twelve hours, whereupon the clear liquor is syphoned off to waste and the remaining solids show-lied out of the settling tank on to an open drying plate l5, which is heated underneath. The heat drives off the moisture out of the mixture, and as the temperature rises, the sawdust ignites and slowly burns, causing the metal to be sweated out. The drying plate is preferably on an incline so that the free metal runs oil the lower end of the plate into a receptacle from whence it may be cleaned by remelting. if necessary, and run into molds.

The dross, or ashes, resulting from the drying step, is next passed through a magnetic separator I6 to remove the metallic iron, which may amount to as much as 6% of the origiml mass of scruff. The remaining dross or ashes, consisting principally oi the oxides of the plating metal and mounting to only about 12% of the original charge of scruiI, is sent to a reverberatory iurnace. In this respect my improved process is a distinct improvement over priorart processes known to me, in that the percentage of the semi! given expensive furnace treatment is greatly reduced.

In the furnace around 35 pounds of soda ash and a suflicient amount of carbon to reduce the metal oxides, preferably in the: form of rice anthracite, is added, and the temperature so regulated as to reduce the oxides to metal, which is recovered in the usual manner. i 7 a By means of my improved process'I have, in actual practice, greatly reduced the cost o1 metal recovered, overcome the difficulty due to stoppage oi flues, such as is encountered in a scruil' furnace, and have increased the recovery of metal from the semi! approximately 10%. While I have de-' scribed my invention as beingapplicable to the recovery of terne metal, it will be obvious that it may be used in the recovery of other metals, for example, from the semi! and residues collected in the tin plate process.

While I have shown my inventionin but one form, it will be obvious to those skilled in the art thatit'is not so limited,'bu t is susceptible of various changes'and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

l. The process 01' recovering tin and terne metal from scrufl' which comprises reacting the scruff with a hot alkali solution to saponify the saponifiable oils and greasestherein, said solution containing around 1.5% of a. soluble mineral oil, separating scum and saponified matter from the solution, allowing the remaining solids to settle outof the solution and draining on the solution, drying and burning the said solids in open air to sweat out the free metal, separating metallic iron from the resultant ash, and reducing the oxides in the remaining ash to metal.

, 2. The process of recovering tin and terne "metal from scrufi which comprises reacting the scruff with a hot alkali solution to saponify the saponiilable oils and greases therein, separating scum and saponified matter, .from the solution, :atllovving the rern'ainingrsolids to settle out of the solution and draining oil. the solution, drying and burning the said solids in open air to sweat out the free metal, separating metallic iron from the resultant ash, and reducingthe oxides in the remaining ashto metal. WILLIAM J, BULLOCK. 

